1. Field of the Invention
The present invention relates to a recording apparatus having an inkjet recording head.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2006-44021 discloses a printer including a plurality of inkjet recording heads arranged along a sheet conveying direction, in which humidified gas is supplied to an area near ink nozzles so as to prevent drying of the nozzles. By filling the gaps between the recording heads with support members and making the recording heads and the support members coplanar, a continuous narrow gap region having a predetermined length is formed. By supplying highly humidified gas to this gap region, each recording head is moisturized and prevented from drying. A unit that produces humidified gas has a single humidification chamber. For example, an ultrasonic vibrator, a heater, or an evaporation filter is used for generating water vapor.
The recording heads to be humidified face a sheet conveying path. Therefore, openings through which a sheet moves in and out are necessary, and the gap region cannot be an enclosed space. For this reason, in order to perform necessary humidification, humidified gas produced in the humidification unit and supplied to the space is required to have an extremely high humidity, for example, a specific humidity of approximately 0.02019 to approximately 0.02722 [kg/kgDA]. However, a humidification unit having a structure such as that disclosed in Japanese Patent Laid-Open No. 2006-44021 needs to be very large in order to produce humidified gas having the necessary humidity. This increases the size of the entire recording apparatus and power consumption.
In the apparatus of Japanese Patent Laid-Open No. 2006-44021, a sheet is held and conveyed by an attraction belt or an attraction roller, and the reverse side of the sheet is attracted and held by an electrostatic attraction technique or a vacuum attraction technique. Because only the reverse side of the sheet is held, the sheet may be poorly attracted depending on the type and property of the sheet. In particular, in the apparatus of Japanese Patent Laid-Open No. 2006-44021, highly humidified gas is blown to the attraction belt or the attraction roller, and therefore charges dissipate from the attraction surface due to the humidity, and the force that holds the sheet is significantly reduced. Therefore, if the sheet has a high stiffness and is strongly curled, the sheet cannot be completely held just by attracting the reverse side of the sheet, and the sheet is partly out of contact with the attraction belt or the attraction roller. In the part being out of contact with the attraction belt or the attraction roller, the quality of an image recorded thereon is decreased. If the part is significantly away from the attraction belt or the attraction roller, the sheet may be brought into contact with the recording heads. If a vacuum attraction technique is used in order to hold the sheet in the apparatus of Japanese Patent Laid-Open No. 2006-44021, vacuum sucks humidified gas before attracting the sheet, and therefore humidification efficiency is very low.